Vehicle fuel tanks generally include a filler neck extending from the tank to allow a user to refill the tank with liquid fuel. Some type of cap or cover is placed over the filler neck in order to seal the fuel tank from the atmosphere. Conventional gas cap assemblies are typically threaded onto the filler neck and include some type of locking handle. The typical function of a gas cap is to seal the fuel tank from outside impurities, such as dirt and dust, and to also maintain fuel vapor within the fuel tank. A predetermined pressure is usually maintained by a valve mechanism located within the cap. When the pressure within the fuel tank reaches a predetermined super-atmospheric level, the valve mechanism automatically opens to release the pressure. When the pressure within the fuel tank drops to a predetermined sub-atmospheric level, the valve mechanism opens to equalize the pressure.
Before the filling of the fuel tank a user completely removes the gas cap from the filler neck and then inserts a filling nozzle. The fuel tank is then filled to the desired level. As appreciated, pressure may build-up within the fuel tank but still be below the super-atmospheric level.
Many prior art refueling systems include a sealing flap door mounted within the filler neck. The filling nozzle opens the flap door when inserted into the filler neck. When the flap door is closed, the flap door seals the filler neck from the atmosphere and contains the built-up pressure within the fuel tank. Just before insertion of the filling nozzle, some fuel may drip or spill from the filling nozzle onto the flap door. This creates a potentially dangerous situation. Specifically, when the filling nozzle opens the flap door, the seal between the flap door and filler neck is broken which releases the built-up pressure in the fuel tank. This escaping vapor can spray the spilled fuel toward the user. Certain injury can result such as affixation, burning and scorching.
Accordingly, it is desirable to have a fuel refilling assembly which incorporates a fast pressure decay within the fuel filler neck and fuel tank prior to completely inserting the filling nozzle. Even more preferably, this pressure decay should automatically be triggered when the filling process is initiated by the user. In addition, the fuel refilling assembly may also incorporate a valve mechanism for automatically equalizing the pressure within the fuel tank.